如何编写显示与用户时区相关的每月HTML警报

var userOffset = new Date().getTimezoneOffset();

var currentDate = new Date();
currentDate.setDate(1);
var nextMonth = new Date(currentDate.getFullYear(), currentDate.getMonth() + 1, 1);
nextMonth.setDate(nextMonth.getDate() - 1);

var startDate = currentDate.toISOString().split('T')[0];
var endDate = nextMonth.toISOString().split('T')[0];

var userTimezone = Intl.DateTimeFormat().resolvedOptions().timeZone;

var alertHTML = '<div class="alert">\
                    <h3>Monthly Alert</h3>\
                    <p>Timezone: ' + userTimezone + '</p>\
                    <p>Start Date: ' + startDate + '</p>\
                    <p>End Date: ' + endDate + '</p>\
                </div>';

document.getElementById('alertContainer').innerHTML = alertHTML;